Parkinson's Drug Reverses Age-Related Mental Declines

A drug widely used to treat Parkinson's disease has been found to help to reverse age-related mental declines in some older people, improving their ability to make good decisions.

Researchers from the Wellcome Trust Centre for Neuroimaging found seniors given L-DOPA (Levodopa) — a drug that increases levels of dopamine in the brains of Parkinson's patients — helped improve their decision-making skills by boosting activity in a region of the brain linked to learning and judgment.

The study, published in the journal Nature Neuroscience, also identified changes in the patterns of brain activity of adults in their seventies that help to explain why many seniors have a harder time making sound decisions than younger people.

"We know that dopamine decline is part of the normal aging process so we wanted to see whether it had any effect on reward-based decision making,” said lead researcher Rumana Chowdhury, M.D. “We found that when we treated older people who were particularly bad at making decisions with [L-DOPA] their ability to learn from rewards improved to a level comparable to somebody in their twenties and enabled them to make better decisions."

The researchers noted that poorer decision-making is a natural part of the aging process that stems from a decline in the brain’s ability to learn from experiences and predict the likelihood of getting a reward from the choices that we make.

Past research has shown that an area of the brain called the nucleus accumbens, which is involved in that process, is affected by dopamine.

For the study, researchers tracked decision-making processes in 32 healthy seniors and compared them to those of 22 other volunteers in their twenties. Older participants were tested on and off with L-DOPA as they completed a behavioral learning task that mirrors the decisions gamblers make while playing slot machines. Researchers tracked the brains of the partiticipants and assessed their performance before and after drug treatment.

The results showed seniors who performed best in the gambling game before drug treatment had greater "integrity" of the dopamine pathways in their brains. Older adults who performed poorly before drug treatment also did significantly better after taking L-DOPA.

"The older volunteers who were less able to predict the likelihood of a reward from their decisions, and so performed worst in the task, showed a significant improvement following drug treatment," Dr. Chowdhury explained.

John Williams, M.D., head of Neuroscience and Mental Health at the Wellcome Trust, said the findings have broad implications for treating age-related mental declines in seniors.

"This careful investigation into the subtle cognitive changes that take place as we age offers important insights into what may happen at both a functional and anatomical level in older people who have problems with making decisions,” Dr. Williams said. “That the team were able to reverse these changes by manipulating dopamine levels offers the hope of therapeutic approaches that could allow older people to function more effectively in the wider community."

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